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Occup Environ Med. 2007 December; 64(12): 856.
PMCID: PMC2095391

The confounding effects of intra‐oral metals in salivary biomarkers

In their Education article in the March issue (Occup Environ Med 2007;64:202–10), Koh and Koh interestingly propose that measurements of heavy metals (for example, lead and cadmium) in saliva may be a novel and promising approach to occupational health, revealing the patient's risk of systemic exposure to toxicants. We would like to share our experience regarding the assessment of metals in saliva matrices.1,2,3

It is well known that intra‐oral metallic dental restorations release various trace elements into saliva, including lead and cadmium.1,3,4,5 The metal‐matrix alloy of dental amalgam fillings may contain approximately 3.4 µg/g of lead and 4.5 µg/g of cadmium (unpublished data), and fillings are therefore a potential source of these elements. However, other dental alloy restorations may also release these metals.

Dental microwear, oral corrosion and galvanic currents are considered the three fundamental factors which trigger the release of a metal into the saliva.1,2,3 The release of intra‐oral metals into the saliva from dental alloy restorations may explain the apparent differences between previous studies about the use of salivary heavy metals as biomarkers (Koh and Koh).6

Even more importantly, a variable associated with the risk of inadvertent contamination of saliva during handling may come from wearing workers' protective gloves. Upon contact with metals during handling, metal dust and fumes can contaminate the gloves, clothing and skin of occupationally‐exposed personnel. In turn, these items may come into contact with the mouth, leading to falsely elevated results in saliva measurements.

In order to assess occupational exposure to metals, other validated outcomes measures such as lead and cadmium concentrations in both blood and urine are currently available.7 We suggest that estimates of lead and cadmium in saliva are potentially confounded by the release of intra‐oral metals and unintentional contamination, which should be taken into account.


Competing interests: None declared.


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2. Guzzi G, Minoia C, Pigatto P D. et al Methylmercury, amalgams, and children's health. Environ Health Perspect 2006. 114149 [PMC free article] [PubMed]
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6. Nriagu J, Burt B, Linder A. et al Lead levels in blood and saliva in a low‐income population of Detroit, Michigan. Int J Hyg Environ Health 2006. 209109–121.121 [PMC free article] [PubMed]
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